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\begin{document}

\title{Retroauricular hairline approach versus conventional approach for
submandibular gland resection: a meta-analysis}



\author[1]{Wanyu Liu}%
\author[1]{Lei Zhu}%
\author[1]{Wenhan Yang}%
\author[1]{Zilu Meng}%
\author[1]{Yudong Wang}%
\affil[1]{The First Affiliated Hospital of Guangdong Pharmaceutical University}%


\vspace{-1em}



  
  \date{June 13, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
\textbf{Background and Objectives:} The retroauricular hairline approach
is increasingly being used for submandibular gland resections because of
the excellent cosmetic results. A meta-analysis of studies compared the
retroauricular hairline and conventional approaches for submandibular
gland excision. \textbf{Methods:} A meta-analysis of studies identified
from the PubMed, Embase, and China National Knowledge Infrastructure
databases was performed. Postoperative nerve damage (temporary earlobe
numbness and other signs of nerve damage), surgical durations, wound
lengths, intraoperative bleeding volumes, postoperative drainage, and
lengths of hospital stay were compared. \textbf{Results:} The
retroauricular hairline approach led to greater risk of temporary
earlobe numbness (OR: 7.28; 95\% CI: 1.57--33.87; P = 0.01), but this
resolved during the follow-up. There was no significant difference in
the risk of other nerve injuries between the two approaches. The
retroauricular hairline group had significantly longer operative times
and wound lengths compared to the conventional resection group. There
were no significant differences between the two approaches in
intraoperative bleeding volumes, postoperative drainage, and lengths of
hospital stay. \textbf{Conclusions:} The retroauricular hairline
approach is a safe and efficient alternative to the conventional
approach. It provides better cosmetic results and does not increase the
risk of long-term neurological complications.%
\end{abstract}%



\sloppy


\textbf{Title Page}

\textbf{Title:} Retroauricular hairline approach versus conventional
approach for submandibular gland resection: a meta-analysis

\textbf{Running title:} Submandibular gland resection approaches

\textbf{Authors:}

Wanyu Liu\textsuperscript{1}, Lei Zhu\textsuperscript{2}, Wenhan
Yang\textsuperscript{3}, Zilu Meng\textsuperscript{4}, Yudong
Wang\textsuperscript{*},

*\textbf{Corresponding author}

\textbf{Name, address, telephone, and E-mail of authors}

Wanyu Liu\textsuperscript{1}, Master

Address:The First Affiliated Hospital of Guangdong Pharmaceutical
University, No.19, Nonglinxia Road, Yuexiu District, Guangzhou, China.

Email: \emph{liuwanyu2009@163.com}; Tel: +8619868388652

ORCID iD:liuwanyu2009@163.com

Lei Zhu\textsuperscript{2}, Master

Address:The First Affiliated Hospital of Guangdong Pharmaceutical
University, No.19, Nonglinxia Road, Yuexiu District, Guangzhou, China.

Email: \emph{1823987842@qq.com}; Tel: +8615629091002

ORCID iD:\emph{1823987842@qq.com}

Wenhan Yang\textsuperscript{3}, Master

Address:The First Affiliated Hospital of Guangdong Pharmaceutical
University, No.19, Nonglinxia Road, Yuexiu District, Guangzhou, China.

Email: \emph{1285861331@qq.com}; Tel: +8618750769869

ORCID iD:\emph{1285861331@qq.com}

Zilu Meng\textsuperscript{4}, Master

Address:The First Affiliated Hospital of Guangdong Pharmaceutical
University, No.19, Nonglinxia Road, Yuexiu District, Guangzhou, China.

Email: \emph{qianqian4821@qq.com}; Tel: +8616639631519

ORCID iD:\emph{qianqian4821@qq.com}

*Yudong Wang, MD

Address:The First Affiliated Hospital of Guangdong Pharmaceutical
University, No.19, Nonglinxia Road, Yuexiu District, Guangzhou, China.

Email: dong3295@139.com; Tel: +8613922231826; Fax: +86-61325337

ORCID iD:dong3295@139.com

\textbf{Funding}

This research did not receive any specific grant from funding agencies
in the public, commercial, or not-for-profit sectors.

\textbf{Competing interests}

The authors declare that they have no conflicts of interest.

\textbf{Ethical approval}

Not applicable.

\textbf{Patient consent}

Not applicable.

\textbf{Synopsis for Table of Contents.}

1. Submandibular gland resection is commonly performed for salivary
gland tumors. 2. We pay more attention to the comparison of
postoperative neurological damage. 3. People's requirements for
postoperative beauty are becoming increasingly high.

\textbf{Title:} Retroauricular hairline approach versus conventional
approach for submandibular gland resection: a meta-analysis

\textbf{Abstract}

\textbf{Background and Objectives:} The retroauricular hairline approach
is increasingly being used for submandibular gland resections because of
the excellent cosmetic results. A meta-analysis of studies compared the
retroauricular hairline and conventional approaches for submandibular
gland excision.

\textbf{Methods:} A meta-analysis of studies identified from the PubMed,
Embase, and China National Knowledge Infrastructure databases was
performed. Postoperative nerve damage (temporary earlobe numbness and
other signs of nerve damage), surgical durations, wound lengths,
intraoperative bleeding volumes, postoperative drainage, and lengths of
hospital stay were compared.

\textbf{Results:} The retroauricular hairline approach led to greater
risk of temporary earlobe numbness (OR: 7.28; 95\% CI: 1.57--33.87; P =
0.01), but this resolved during the follow-up. There was no significant
difference in the risk of other nerve injuries between the two
approaches. The retroauricular hairline group had significantly longer
operative times and wound lengths compared to the conventional resection
group. There were no significant differences between the two approaches
in intraoperative bleeding volumes, postoperative drainage, and lengths
of hospital stay.

\textbf{Conclusions:} The retroauricular hairline approach is a safe and
efficient alternative to the conventional approach. It provides better
cosmetic results and does not increase the risk of long-term
neurological complications.

\par\null

\textbf{Keywords:} retroauricular approach, submandibular gland,
aesthetic, gland-preserving surgery

\textbf{Introduction}

In recent decades, head and neck surgery has made great strides with the
development and improvement of various minimally-invasive surgical
techniques. These procedures have significantly improved survival rates,
patient satisfaction, and quality of life. Head and neck surgery has
been slow to adopt minimally-invasive surgical techniques because of the
complex anatomy, limited operating space, and multiple contiguous layers
and cavities in this region\textsuperscript{1}. Technological
developments in endoscopic and robotic surgery have led to significant
advances in minimally-invasive surgery in all surgical fields, including
head and neck surgery\textsuperscript{2-5}. These surgical techniques
eliminate the need for large, visible neck incisions and efficiently
restore the function. They can also achieve improved aesthetic outcomes
with an acceptable cost and complication rates equal to or lower than
those for conventional surgery.

Submandibular gland resection is commonly performed for salivary gland
tumors, recurrent submandibular adenitis, and salivary sialolithiasis.
Traditional submandibular gland resection through a cervical incision is
a safe procedure with a low risk of nerve damage, but has the major
disadvantage of postoperative scar formation\textsuperscript{6}. Several
surgical approaches, including intraoral, endoscopic cervical, and
retroauricular hairline approaches, have aimed to improve the cosmetic
results of the procedure\textsuperscript{7-10}. Despite perfect cosmetic
results, the intraoral approach has been shown to cause lingual nerve
palsy and limited tongue movements as a result of scar
contracture\textsuperscript{8, 11}. Although the endoscopic neck
approach requires a smaller incision, the resultant scar is still
visible and there may be pimple formation in keloid patients. The
retroauricular hairline approach has a longer incision, but it is
perfectly hidden in the hairline behind the ear\textsuperscript{12}.

This study presents our experience with the esthetic and safety aspects
of submandibular gland resection through the retroauricular hairline
approach. The meta-analysis demonstrates the safety and esthetic
advantages of this approach, along with the potential risk of temporary
earlobe numbness, which resolves during the follow-up. Submandibular
gland excision through the retroauricular hairline approach had a
similar incidence of permanent postoperative complications and improved
cosmetic results compared to the traditional approach.

\textbf{Materials and methods}

2.1 Search strategy

The PubMed, Embase, and China National Knowledge Infrastructure
databases were systematically searched for articles published before
January 2023. The following keywords were used to search for comparisons
between retroauricular hairline and conventional approaches in
submandibular gland excision patients: ``submandibular gland'',
``submandectomy'', ``retroauricular approach'', ``aesthetic'', and
``gland-preserving surgery''. The search was expanded using the related
literature function. All retrieved abstracts, articles, and citations
were reviewed regardless of the language of publication.

2.2 Inclusion and exclusion criteria

Studies comparing the retroauricular and conventional approaches in
patients undergoing submandibular adenotomy were included if an adequate
description of the surgical technique and at least one quantitative
outcome metric were reported. Patients with a history of neck surgery or
radiotherapy, clinical signs of extra-glandular tumor infiltration,
metastatic disease requiring concomitant neck dissection, and those with
possible contraindications to surgery or general anesthesia based on the
preoperative evaluation were excluded.

2.3 Data extraction

Data were independently extracted by two investigators who read the
abstracts and full texts to identify the studies that met the inclusion
criteria. Disagreements between the investigators were resolved through
discussion. The following data were collected from each study: first
author, year of publication, type of study, number of patients for each
procedure, and complications.

2.4 Quality assessment

Study quality was assessed using the Newcastle-Ottawa Scale (NOS), which
is based on three factors: patient selection, comparability of study
groups, and number of reported outcomes. Study quality was indicated
using the NOS star system. Each item received a maximum of one star,
except items related to comparability, which could receive two stars.
NOS scores range from 0 to 9 stars, with scores \textgreater{} 4
indicating high-quality studies\textsuperscript{13}.

2.5 Statistical analysis

Meta-analyses were performed by using Review Manager version 5.2
(Cochrane Collaboration) and Stata SE version 12.0 (StataCorp LLC,
College Station, TX, USA). Heterogeneity between groups was assessed
using the \selectlanguage{greek}χ\selectlanguage{english}\textsuperscript{2} test and I\textsuperscript{2} statistics,
and the values were reported as degrees of freedom (df). Heterogeneity
was considered significant if the p-value was \textless{} 0.10 or the I\selectlanguage{ngerman}²
value was \textgreater{} 50\%. This was followed by a random effects or
fixed effects model analysis, whichever was appropriate. Bilateral
p-values \textless{} 0.05 were considered significant
{[}\textsuperscript{14}{]}. Subgroup and sensitivity analyses were
further performed when the heterogeneity was large.

Publication bias was detected using Begg's test and funnel plot
analysis. Bilateral p-values \textless{} 0.05 were considered
significant. Continuity variables were compared using the weighted mean
difference (WMD), and reported with 95\% confidence intervals (CIs).
Dichotomous variables were compared using odds ratios (ORs), and
reported with 95\% CIs. An OR \textless{} 1 favored the retroauricular
approach. If the 95\% CI did not include the value of 1, point estimates
were considered statistically significant at p \textless{}
0.05\textsuperscript{14}.

\textbf{Results}

A total of 294 relevant studies were identified using the PubMed,
Embase, and China National Knowledge Infrastructure databases, and were
imported into the Endnote X8 software (Clarivate PLC, London, UK). After
a review of the titles and abstracts, 56 studies were selected for
in-depth assessment of the full texts. Eight of the studies met the
eligibility criteria and were included in the
meta-analysis\textsuperscript{15-22}. The selection process for the
studies included in the meta-analysis is shown in Fig 1. This study was
conducted strictly in accordance with the PRISMA guidelines.

The studies included four prospective\textsuperscript{15, 17-19}and four
retrospective\textsuperscript{16, 20-22}studies, with a total of 330
patients (186 and 144 for the conventional and retroauricular hairline
approaches, respectively). The main outcome indicators were
postoperative nerve damage, including temporary earlobe numbness (n =
4)\textsuperscript{15, 16, 18, 21} and other signs of nerve damage (n =
7)\textsuperscript{15-21}. The secondary outcome indicators were
duration of surgery (n = 8)\textsuperscript{15-22}, wound length (n =
8)\textsuperscript{15-17, 22}, intraoperative bleeding volume (n =
2)\textsuperscript{16, 22}, postoperative drainage (n =
3)\textsuperscript{18, 19, 22}, length of hospital stay (n =
5)\textsuperscript{15, 17-19, 22}. Because of the good comparability and
clear outcomes of the included studies, all NOS scores were
\textgreater{} 4 stars (Table 1).

\emph{Main outcome indicators}

3.1 Postoperative nerve damage

Seven of the studies described postoperative nerve
damage\textsuperscript{15-21}, which was transient and resolved during
the follow-up. In this meta-analysis, postoperative nerve damage was
divided into transient greater auricular nerve damage and other nerve
damage, including the marginal mandibular branch of the facial nerve,
lingual nerve, and hypoglossal nerve. Transient auricular nerve damage
mainly manifested as temporary earlobe numbness. Damage to the marginal
mandibular branch of the facial nerve, lingual nerve, and hypoglossal
nerve was indicated by crookedness of the corners of the mouth, tongue
tip numbness, and tongue deviation on extension, respectively.

3.1.1 Temporary earlobe numbness

Four of the eight studies reported the occurrence of temporary
postoperative earlobe numbness\textsuperscript{15, 16, 18, 21}. The
studies included 161 patients; 73 and 88 in the retroauricular hairline
and conventional approach groups, respectively. There were seven cases
of temporary earlobe numbness, all in the retroauricular hairline group.
The difference in temporary postoperative earlobe numbness between the
two surgical approaches was statistically significant (OR: 7.28; 95\%
CI: 1.57--33.87; P = 0.01; Fig. 2). There was no significant
heterogeneity among the studies (\selectlanguage{greek}χ\selectlanguage{english}\textsuperscript{2} = 0.16, df = 3, P
= 0.98, I\textsuperscript{2} = 0\%; Fig. 2). This indicated that
submandibular gland excision through the retroauricular hairline
approach increases the risk of temporary earlobe numbness, but this
resolves during the follow-up.

3.1.2 Other nerve damage

Transient damage to the marginal mandibular branch of the facial nerve,
lingual nerve, and hypoglossal nerve was described in seven of the
studies\textsuperscript{15-21}, with a total of 270 patients; 114 and
156 in the retroauricular and conventional approach groups,
respectively. There was no statistically significant difference between
the two surgical approaches (OR: 0.80; 95\% CI: 0.38--1.71; P = 0.57;
Fig 3). This indicates that the two surgical approaches had similar
incidences for damage to the marginal mandibular branch of facial nerve,
lingual nerve, and hypoglossal nerve. The incidences of nerve injury in
both the conventional and retroauricular groups in the Carlos 2019 study
{[}20{]} were close to 50\%, however, all symptoms disappeared during
the follow-up period. When the results of this study were excluded, the
results remained statistically insignificant between the two surgical
approaches (OR: 0.77; 95\% CI: 0.24--2.40; P = 0.65; Fig 12).

\emph{Secondary outcome indicators}

Surgical duration

Eight studies\textsuperscript{15-22} described the surgical duration for
submandibular gland resection through the retroauricular hairline
approach. A total of 330 patients underwent submandibular gland
resections; 144 through the retroauricular hairline approach and 186
through the conventional approach. The surgical duration for the
retroauricular hairline approach was significantly longer than that for
the conventional approach (WMD: 27.26; 95\% CI: 6.35--48.18; P = 0.01;
Fig. 5), and there was significant heterogeneity among the studies (\selectlanguage{greek}χ\selectlanguage{english}2 =
613.23, df = 7, P = 0.01, I2 = 99\%; Fig. 5). Visual assessment of the
funnel plot indicated a slight publication bias. However, the Egger's
test was not statistically significant (p = 0.126) (Fig 6).

3.3 Wound length

Four of the studies\textsuperscript{15-17, 22} described the wound
length in 126 patients; 62 and 64 in the retroauricular and conventional
approach groups, respectively. The retroauricular hairline group had
significantly longer wound lengths compared to the conventional group
(WMD: 4.65; 95\% CI: 1.94--7.36; P = 0.0008; Fig. 7). There was
significant heterogeneity among the studies (\selectlanguage{greek}χ\selectlanguage{english}\textsuperscript{2} =
120.03, df = 3, P = 0.0008, I\textsuperscript{2} = 98\%; Fig. 7).

3.4 Intraoperative bleeding

Intraoperative bleeding volume was described in two of the
studies\textsuperscript{16, 22}, with a total of 88 patients; 43 and 45
in the retroauricular and conventional approach groups, respectively.
There were no statistically significant differences between the two
surgical approaches (WMD: -7.39; 95\% CI: -28.40--43.61; P = 0.49; Fig
8). There was significant heterogeneity among the studies
(\selectlanguage{greek}χ\selectlanguage{english}\textsuperscript{2} = 28.85, df = 1, P = 0.00001,
I\textsuperscript{2}= 97\%; Fig. 8).

3.5 Postoperative drainage

Postoperative drainage was described in three of the
studies\textsuperscript{18, 19, 22}, with a total of 130 patients; 64
and 66 in the retroauricular hairline and conventional approach groups,
respectively. Data pooling showed no significant differences in
postoperative drainage between the two approaches (WMD: 17.49; 95\% CI:
-4.36--39.34; P = 0.12; Fig 9). There was significant heterogeneity
among the studies (\selectlanguage{greek}χ\selectlanguage{english}\textsuperscript{2} =28.93, df = 2, P<0.00001,
I\textsuperscript{2} = 93\%; Fig. 9).

3.6 Length of hospital stay

Five of the studies reported the duration of
hospitalization\textsuperscript{15, 17-20, 22}. A total of 168 patients
underwent submandibular gland resection; 83 and 85 through the
retroauricular hairline and conventional approaches, respectively. The
results showed no significant difference in the number of hospital days
between the two groups (WMD: -0.25; 95\% CI: -0.99--0.49; P = 0.51; Fig
10).

3.7 Cosmetic effects

Two of the studies {[}15-16{]} described cosmetic effects using a visual
analogue scale (VAS) in 58 patients, 28 and 30 in the retroauricular and
conventional approach groups, respectively. The VAS uses objective
content satisfaction scores on a scale of 0--10; the higher the score,
the higher the satisfaction level. The retroauricular hairline group had
significantly better cosmetic effects than the conventional group. The
difference in cosmetic effects between the two surgical approaches was
statistically significant (WMD: 3.83; 95\% CI: 2.50--5.16; P<0.00001;
Fig 11). There was greater heterogeneity among the studies
(\selectlanguage{greek}χ\selectlanguage{english}\textsuperscript{2} =2.62, df = 1, P = 0.11, I\textsuperscript{2} =
62\%; Fig. 11).

3.8 Subgroup analysis

Only two of the studies reported the intraoperative bleeding
volume\textsuperscript{16, 22}, which made it difficult to perform a
subgroup analysis. Furthermore, postoperative drainage and cosmetic
effects were not reported adequately to perform a subgroup analysis.

3.8.1 Open submandibular gland excision Compared to the original
analysis, there were no significant differences in the subgroup analysis
for surgical durations of open submandibular gland excision through the
two approaches (WMD: 0.60; 95\% CI: -18.00--19.20; P = 0.95; Fig 5).
3.8.2 Endoscopic submandibular gland excision

Compared to the original analysis, the subgroup analysis was consistent
with the original data analysis for surgical duration (WMD: 30.83; 95\%
CI: 7.39--54.27; P = 0.010; Fig 5), wound length (WMD: 5.76; 95\% CI:
5.22--6.29; P \textless{} 0.00001; Fig 7), and length of hospital stay
(WMD: -0.77; 95\% CI: -2.20--0.67; P = 0.30; Fig 10).

3.8.3 Robotic submandibular gland excision

Compared to the original analysis, there were no significant differences
in the subgroup analysis for surgical duration between the two groups
(WMD: 48.24; 95\% CI: -14.27--110.75; P = 0.13; Fig 5). 3.9 Sensitivity
analysis

To evaluate the robustness and reliability of our results, we performed
a sensitivity analysis. For articles with a significant percentage, we
excluded and re-analyzed the data.

3.9.1 Forest plot and meta-analysis for temporary injury to other
nerves.

In this study by Carlos et al, there was a significantly higher
proportion of the outcome metric of temporary injury to other nerves
than in other literature. After excluding this study, the outcome was
consistent with the original data analysist (OR: 0.77; 95\% CI:
0.24--2.40; P = 0.65; Fig. 12). This was consistent with the original
consolidated results and showed that the results were stable.

\textbf{Discussion}

This meta-analysis included four prospective and four retrospective
studies, with a total of 330 patients, comparing the retroauricular
hairline and conventional approaches for submandibular gland resection.
The retroauricular hairline approach was found to be safe, with better
cosmetic results and similar risk of postoperative nerve damage compared
to the conventional approach. There was no significant difference in the
intraoperative bleeding volume, postoperative drainage, and length of
hospital stay between the two approaches.

Minimally-invasive surgical techniques emerged in the 1980s, and are now
used in various surgical specialties, including abdominal, thoracic, and
gynecological surgery. In recent years, head and neck surgery has made
great strides in minimally-invasive surgery, aiming for improved
esthetics, reduced blood loss, shorter hospital stays, and fewer
complications\textsuperscript{23, 24}. Technological developments and
the demand for improved esthetics have changed the choice of surgical
modalities for submandibular gland removal. The patients also expect
perfect cosmetic results after submandibular gland surgery.
Submandibular gland removal through the transcervical approach may
result in unsightly keloids or hyperplastic scarring. This has led to
the development of various techniques, including intraoral and
retroauricular approaches, to reduce scar formation. Traditional
submandibular gland resection is performed through a transcervical
approach, which is a relatively safe procedure, but can lead to
postoperative neurological complications. In young individuals, the scar
is visible on the exposed part of the neck, which is cosmetically
undesirable, particularly in cases of keloid formation. This places a
tremendous burden on the patients and can have negative psychological
and social effects. Based on the cosmetic requirements,
minimally-invasive approaches for submandibular gland removal, including
the transoral endoscopic approach\textsuperscript{25}, smaller incisions
combined with endoscopic assistance, and retroauricular hairline
approach, have been investigated in the recent years. Intraoral
submandibular gland surgery was described several years ago, but had
limited applicability. Although intraoral surgery results in perfect
cosmetic outcomes, it requires a higher level of surgical expertise, and
the narrow surgical field can make it difficult to ligate the facial
artery. This has limited the wider application of this approach, but it
has been reintroduced in recent years with the development of
robot-assisted surgery {[}\textsuperscript{26}{]}. Despite the reduced
length of neck incision, an important disadvantage of small neck
incisions combined with endoscopy is the high level of surgical
expertise required to handle the endoscope. Surgeons must be accustomed
to endoscopic surgical views, and be able to handle a wide variety of
instruments, including endoscopes, grasping forceps, harmonic scalpels,
etc. In terms of cosmetic results, the posterior auricular approach
offers significant advantages compared to conventional submandibular
gland resection.

This meta-analysis demonstrates the feasibility of retroauricular
hairline approach for submandibular gland resections. Although the
retroauricular incision line is approximately 4--6 cm longer than the
traditional transcervical incision, a ``scarless'' effect is achieved
because the scar is hidden behind the ear and in the hairline,
especially when covered by long hair. This meta-analysis compared the
operative times, wound lengths, intraoperative bleeding volumes,
postoperative drainage, durations of hospital stay, and postoperative
nerve injuries between the postauricular hairline and conventional
approaches for submandibular gland resection. The operative time and
wound length were longer in the postauricular group compared to the
conventional group. However, there were no statistically significant
differences in the intraoperative bleeding volumes, postoperative
drainage, and lengths of hospital stay between the approaches. The
retroauricular hairline group had a higher risk of earlobe numbness, but
this resolved during the follow-up period. There were no differences in
the risk of damage to other nerves between the two approaches. The
present meta-analysis had several limitations. First, half of the
included studies were cohort studies; further prospective randomized
controlled studies are needed to increase the level of evidence. Second,
the differences in the study populations, surgical skill levels, and
other factors could have contributed to heterogeneity among the studies.
In the present study, the heterogeneity for continuous variables was
greater than that for dichotomous variables, so we performed subgroup
and sensitivity analyses. The subgroup analysis for the postauricular
hairline group was performed by dividing the procedures into open,
endoscopic, and robotic surgeries. There was significant heterogeneity
in the surgical duration among the open, endoscopic, and robot-assisted
retroauricular hairline submandibular gland resection subgroups. The
heterogeneity was greater when the three groups were combined
(I\textsuperscript{2} = 99\%; Fig 2), indicating that grouping factors
may not be the source of heterogeneity. In terms of wound lengths
(I\textsuperscript{2} = 99\%), there was no heterogeneity in the
subgroup analysis for the endoscopic retroauricular hairline approach
(I\textsuperscript{2} = 0\%; Fig 3). This indicates that grouping
factors may be the source of heterogeneity. Comparing the lengths of
hospital stay between the two approaches (I\textsuperscript{2} = 89\%;
Fig 6), subgroup analysis revealed no heterogeneity for the
robot-assisted retroauricular hairline submandibular gland resection
(I\textsuperscript{2} = 0\%). However, the heterogeneity was greater in
the endoscopic group, indicating that subgroup factors may be the source
of heterogeneity. Meanwhile, intraoperative bleeding volumes and
postoperative drainage were more heterogeneous, but could not be
analyzed in subgroups because of insufficient data. This was another
important limitation of this meta-analysis.

This study showed that submandibular gland excision by the
retroauricular hairline approach had significantly higher postoperative
cosmetic outcome scores than the traditional approach; the
retroauricular hairline group patients under the age of 30 years had
four times higher postoperative cosmetic outcome scores than the
traditional group\textsuperscript{21}. This difference may be
significant for patients with a cicatricial constitution. The
retroauricular approach was also safer than the traditional cervical
incision because no large neck vessels become exposed if sutures are
lost, leading to necrosis or rupture, which prevents the risk of
catastrophic bleeding\textsuperscript{27}. However, surgeons may be
uncomfortable with the top-to-bottom anatomical orientation for the
retroauricular approach, and the limited access and visibility for
anterior lesions. Although endoscopic surgery provides a magnified of
the narrow surgical space, the assistant must keep the endoscope in
place and move it in concert with the surgeon's movements. This requires
a close and skilled coordination between the assistant and surgeon.
Robotic submandibular gland resection solves this problem as the surgeon
controls the two robotic arms remotely from a console to perform the
procedure. However, robotic and endoscopic submandibular gland
resections were found to have comparable surgical and cosmetic
outcomes\textsuperscript{28}. With the advent of artificial
intelligence, robotic surgery is emerging as a viable alternative to
traditional open surgery, with potential safety and esthetic advantages.
De Virgilio proposed that the first step in robotic submandibular gland
resection through the retroauricular incision was to identify and ligate
the facial artery and other major arterial and venous branches. This
minimizes the risk of bleeding and improves visibility, further
demonstrating that a large incision does not necessarily lead to poorer
postoperative outcomes\textsuperscript{10}. The robotic retroauricular
hairline approach reduces the incidence of surgical complications
associated with the postauricular anatomy because it does not require
the creation of a surgical tunnel and postauricular flap elevation. It
also reduces the risk of postoperative complications, including seromas
and hematomas, caused by flap elevation. Because the robotic system is
equipped with a magnifying camera and dexterous instruments, the gland
boundaries are clearly identifiable, which facilitates the submandibular
gland stripping and excision\textsuperscript{29}. However, the use of
robotic systems is technically demanding. The advantages of the
retroauricular hairline approach are based on a smaller incision along
the hairline. The large robotic arms of the currently available systems
make the docking process critical, which makes the surgical technique
and placement of robotic instruments more difficult. Without proper arm
positioning, frequent collisions of surgical instruments may occur,
making the procedure more time consuming and
difficult\textsuperscript{30}. The robotic systems are expensive and not
widely available, particularly in developing countries. Although cost
comparison was not done in the present study, it may be a deciding
factor for the clinical application of robotic surgeries. Considering
the economic realities of most countries, the endoscopic technique may
be a more feasible alternative to conventional surgery for the
optimization of esthetic and functional outcomes in selected head and
neck tumor patients.

\textbf{Conclusions}

Submandibular gland resection by retroauricular hairline approach
increases the operative time and wound length compared to the
conventional approach. However, there was no significant difference in
intraoperative bleeding volumes, postoperative drainage, and long-term
postoperative nerve damage between the two groups. This meta-analysis
provides a reference for the choice of surgical approach for
submandibular gland resections. The postauricular hairline approach
provides better cosmetic results without increasing the incidence of
long-term postoperative nerve damage. However, the impact of longer
surgical durations and increased risk of temporary earlobe numbness
cannot be ignored. Further studies with larger samples and additional
outcome indicators are required to validate these findings.

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\textbf{Hosted file}

\verb`Figure.docx`  available at \url{https://authorea.com/users/670026/articles/670223-retroauricular-hairline-approach-versus-conventional-approach-for-submandibular-gland-resection-a-meta-analysis}

\textbf{Hosted file}

\verb`Table1.docx`  available at \url{https://authorea.com/users/670026/articles/670223-retroauricular-hairline-approach-versus-conventional-approach-for-submandibular-gland-resection-a-meta-analysis}

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